The roles of plasma proteins in the adhesion of platelets and leukocytes to surfaces of artificial organs will be investigated. Adsorption isotherms for purified human fibrinogen, albumin, and IgG singly, in certain combinations, and in plasma will be constructed. In this work protein adsorption to a series of highly purified and well characterized artificial surfaces will be studies under both static and flow conditions. These studies will permit formation of protein layers of known composition for use in the development of a radioimmunoassay for detection and quantitation of plasma proteins adsorbed to artificial surfaces. Immunospecific rabbit antibodies to certain human plasma proteins will be labeled with 125I and used to detect their respective antigens in the adsorbed protein layers that form on artificial surfaces exposed to blood. A quantitative relationship between protein adsorption and platelet and leukocyte adhesion will be delineated initially in studies of selected artificial surfaces by use of two techniques for quantitation of cell adhesion, the centrifugal force test and the Richardson flow chamber. Eventually material obtained from hemodialyzers and other artificials organs used clinically will be studied in order to quantitate adsorption of specific plasma proteins and correlate this with cell adhesion. These studies are designed to increase our knowledge of the enhancing and inhibiting roles played by plasma proteins in the adhesion of platelets and leukocytes to surfaces of artificial organs.